This contract transferred direct responsibility for completion of toxicity testing of four chemicals at Springborn Institute for Bioresearch, Inc., from a prime contractor to NIEHS. Subchronic and chronic tests of each of the four chemicals, Ampicillin Trihydrate, Penicillin VK, Benzofuran and N,N-Dimethylaniline, using the gavage route of administration in F344 rats and B6C3F1 mice will be performed. These tests will characterize the toxicity associated with subchronic and chronic exposure to these chemicals individually, including target organs, no-effect level, differences in sensitivity between sexes and species, slope of the dose-response curve carcinogenicity.